www.pudn.com > libpmk.rar > uniform-pyramid-maker.h, change:2007-05-27,size:4864b


// Copyright 2007, Massachusetts Institute of Technology.
// The use of this code is permitted for research only. There is
// absolutely no warranty for this software.
//
// Author: John Lee (jjl@mit.edu)
//
// TODO(jjl): what about turning new PointSets with min/max feature
// value beyond min_value_ or max_value_? check for it and add a note in
// the spec.
#ifndef PYRAMIDS_UNIFORM_PYRAMID_MAKER_H
#define PYRAMIDS_UNIFORM_PYRAMID_MAKER_H

#include <vector>
#include <map>
#include <iostream>
#include "pyramids/pyramid-maker.h"
#include "point_set/point-set-list.h"
#include "point_set/point-set.h"
#include "histograms/multi-resolution-histogram.h"

using namespace std;

namespace libpmk {
// Strategy:
// place point into top bin. GetSpaseIndex(0, point) is now 0 of bindex.
// place point into next level. GetSparseIndex(1, point) is now index 1
// of bindex. etc.

/// \brief Creates MultiResolutionHistograms with bins of uniform size at
/// each level.
/**
 * The <tt>discretize_factor</tt> parameter, passed into Preprocess(),
 * is particularly important because it can greatly affect the shape
 * of the resulting pyramid. This parameter multiplies all of the
 * feature values by 10^{discretize_factor}. We typically set it in
 * such a way that the resulting features are on the order of 10^2.
 */
class UniformPyramidMaker : public PyramidMaker {
 public:
   UniformPyramidMaker();

   /// Set parameters and preprocess the pyramid settings.
   /**
    * \param finest_side_length The length of a side of the smallest
    * bin at the lowest level of the pyramid.
    * \param side_factor The length of the side of the bin is this
    * factor larger for bins one level above.
    * \param discretize_factor Scales all of the features by a factor
    * 10^{discretize_factor}.
    * \param do_translations Determines whether to apply random shifts
    * to the bins.
    * \param global_translations Determines whether the shift should be
    * the same across all levels or not.
    * 
    * Rather than preprocessing, ReadFromStream() may be called in
    * lieu of this.
    */
   void Preprocess(const PointSetList& point_sets,
                       double finest_side_length,
                       double side_factor,
                       int discretize_factor,
                       bool do_translations,
                       bool global_translations);

   /// Read parameters and preprocessed data from a stream.
   /**
    * Aborts if the stream is bad.
    */
   void ReadFromStream(istream& input_stream);

   /// Read parameters and preprocessed data from a file.
   /**
    * \sa ReadFromStream
    */
   void ReadFromFile(const char* filename);

   /// Write parameters and preprocessed data to a stream.
   /**
    * Aborts if the stream is bad.
    */ 
   void WriteToStream(ostream& output_stream) const;

   /// Write parameters and preprocessed data to a file.
   /**
    * \sa WriteToStream
    */ 
   void WriteToFile(const char* filename) const;

   /// Get the number of levels in the pyramids that will be created.
   /**
    * Must be called after Preprocess() or ReadFromStream().
    */
   int GetNumLevels() const;

   /// Creates a uniform pyramid from a PointSet.
   /**
    * Requires Preprocess() or ReadFromStream() to be called first.
    * This function allocates memory on its own; it is up to the
    * caller to free the memory. Note that the input point set should
    * not be on the same scale as the point sets that the
    * UniformPyramidMaker was constructed with. If you specified a
    * nonzero <tt>discretize_factor</tt> in the constructor, the
    * PointSet <ps> will automatically be scaled according to that.
    * Additionally, any translations (if you told the constructor to
    * do so) will also be applied automatically-- you should not have
    * to shift or scale anything in <ps> before calling MakePyramid()
    * on it.
    */
   virtual MultiResolutionHistogram* MakePyramid(const PointSet& ps);


 private:
   double finest_side_length_;
   double side_factor_;
   int discretize_factor_;
   int feature_dim_;
   bool do_translations_;
   bool global_translations_;
   bool preprocessed_;

   double min_value_;
   double max_value_;

   double diameter_;
   int num_levels_;

   // One vector per level. This is a num_levels * dim matrix.
   vector<vector<double> > translations_;

   // Make sure that the values (ints) are unique. We need to do this for
   // each level, so it's a vector of size num_levels_ of these mappings from
   // index to int.
   vector<map<LargeIndex, int> > vector_map_;

   // A vector of size num_levels. The ith entry tells you the last-used
   // value in vector_map_.
   vector<int> last_vector_map_values_;

   int GetSparseValue(int level, const LargeIndex& index);
};
}  // namespace libpmk
#endif  // PYRAMIDS_UNIFORM_PYRAMID_MAKER_H